Conventionally, hybrid vehicles including an engine and an electric rotating machine as a power source are known. Further, in this type of hybrid vehicles, there are also known hybrid vehicles provided with a power dividing mechanism capable of distributing input power at a predetermined distribution ratio and outputting the distributed input power.
For example, Patent Literature 1 shown below discloses a hybrid vehicle provided with a differential mechanism (power dividing mechanism) composed of a planetary gear mechanism including a carrier with which an output shaft of an internal combustion engine (engine) is coupled, a sun gear with which a rotating shaft of a first motor/generator (electric rotating machine) is coupled, and a ring gear with which a drive wheel side is coupled. The hybrid vehicle of the Patent Literature 1 is also provided with another differential mechanism in addition to the power dividing mechanism, and the another differential mechanism includes a pinion gear with which the output shaft of the internal combustion engine is coupled and a sun gear with which the rotating shaft of the first motor/generator is coupled via a clutch and is used as a start differential mechanism of the internal combustion engine. When the internal combustion engine of the hybrid vehicle starts, a rotation speed of the rotating shaft of the first motor/generator is reduced by connecting the rotating shaft of the first motor/generator to the start differential mechanism via a clutch and transmitted to the output shaft of the internal combustion engine, and the internal combustion engine is cranked.
Patent Literature 2 shown below discloses a drive system of a hybrid vehicle provided with a distribution mechanism (power dividing mechanism) composed of a planetary gear mechanism including a carrier with which an output shaft of an engine is coupled, a sun gear with which a rotating shaft of a first motor/generator is coupled, and a ring gear with which a rotating shaft of a second motor/generator is coupled as well as the rotating shaft of the second motor/generator is also coupled with a drive wheel side. In the hybrid vehicle of Patent Literature 2, when the engine is started, rotation torque of the first motor/generator is transmitted to the engine via the power dividing mechanism in a state that a vehicle is stopped by a parking brake and the like and the engine is cranked.
Patent Literature 3 shown below discloses a drive system of a hybrid vehicle provided with a power dividing mechanism for distributing power of an engine to a first motor/generator and to a drive wheel side at a predetermined distribution ratio. The drive system employs a planetary cone mechanism capable of changing the distribution rate as the power dividing mechanism. Further, Patent Literature 4 shown below discloses a continuously variable transmission provided with a continuously variable mechanism, which includes balls (rolling members) clamped by an input disc and an output disc and changes a transmission ratio by adjusting a tilt angle of the balls, and a planetary gear mechanism (differential mechanism) with which one of rotating elements is coupled with an output shaft of the continuously variable mechanism. Specifically, Patent Literature 4 describes the planetary gear mechanism configured such that a sun gear as one of the rotating elements is coupled with the output shaft of the continuously variable mechanism, a carrier is coupled with a drive wheel side, and a ring gear is coupled with an output side of a drive force source via a gear group.